Use of liquid dyestuff preparations for dyeing wood

ABSTRACT

This invention relates to a process for dyeing wood with a liquid dyestuff preparation containing  
     (a) 5 to 30% by weight of a dyestuff of the formula (I)  
                 
 
      wherein  
     n 1  and n 2  denote the number 1 or 0,  
     X represents N or CH,  
     Ct +  represents a cation,  
     A, B, G, and D are independently a polyvalent heterocyclic or aromatic radical in which the —(CO)n 1 —O— or —O— are ortho to the respective —N═N— or —N═X—, and  
     (b) 15 to 90% by weight of an alkoxyalcohol of the formula (II) 
     R—O—(-Z-O—) n3 —H  (II) 
      wherein  
     R denotes a straight-chain or branched C 1 -C 4 -alkyl,  
     Z denotes a straight-chain or branched C 2 -C 3 -alkylene, and  
     n 3  represents 1, 2, or 3, and  
     (c) 5 to 75% by weight of water.

[0001] The invention relates to the use of liquid dyestuff preparations for dyeing wood.

[0002] Liquid dyestuff preparations for dyeing wood are usually called woodstains. Woodstains are intended not to mask but to emphasize the grain of the wood and its veneers, giving them colour, and therefore comprise only truly dissolved dyestuffs. Solutions of basic or acidic dyestuffs in water or of solvent dyestuffs in organic solvents are known in practice. In addition to these so-called water-based and solvent-based stains, a combination of these two stains became established at the start of the '80s as a further type. These are water-dilutable solutions of organic dyestuffs in mixtures of water and solvent.

[0003] Woodstains are chiefly employed indoors and serve chiefly for decorative purposes. On application with a sponge, brush or a spray gun, they should penetrate as uniformly as possible and as deeply as possible into the wood material and give a uniform dyeing which is fast to light, water and abrasion after drying. It should furthermore also be possible to protect and preserve the stained wood with clear furniture varnishes without the dyestuffs bleeding out into the clear varnish.

[0004] Woodstains chiefly comprise metal complex dyestuffs.

[0005] It has been found that water-dilutable woodstains which meet the requirements in practice in an outstanding manner are provided with the liquid dyestuff preparations described in the following.

[0006] The invention relates to the use of liquid dyestuff preparations for dyeing wood, characterized in that the liquid dyestuff preparations comprising

[0007] 5 to 30% by weight, in particular 12 to 23% by weight, of a dyestuff of the formula I

[0008]  wherein

[0009] n₁ and n₂ denote the number 1 or 0,

[0010] X represents N or CH, Ct⁺ represents a cation

[0011] and the polyvalent radicals A, B, G and D independently of one another represent heterocyclic or aromatic radicals, in particular optionally substituted phenylene and naphthylene radicals, the particular complexing —COO— or —O— group being in the ortho-position relative to the azo and azomethine group (X═CH) respectively,

[0012] 15 to 90% by weight, in particular 15 to 60% by weight, preferably 20 to 90% by weight, more preferred 25 to 60% by weight, of an alkoxy-alcohol of the formula (II)

R—O—(-Z-O—)_(n3)—H  (II)

[0013]  wherein

[0014] R denotes a straight-chain or branched C₁-C₄-alkyl,

[0015] Z denotes a straight-chain or branched C₂-C₃-alkylene and

[0016] n₃ represents 1, 2 or 3, and

[0017] 5 to 75% by weight of water are employed.

[0018] In general, “liquid” is understood as meaning a liquid state at room temperature under normal pressure.

[0019] In a particular embodiment of the process according to the invention, dyestuff preparations which comprise dyestuffs of the formula (I) which are preferably built up from azo or azomethine compounds which, in the form of their free acid, correspond to the compounds (III) and (IV)

HO—(OC)_(n2)-G-N═X-D-OH  (IV),

[0020] wherein a, B, G, D, n₁ and n₂ have the abovementioned meanings, are employed.

[0021] Preferred dyestuffs of the formula (I) are derived from the following radicals:

[0022] Possible radicals of the formula

[0023] are, preferably:

[0024] Possible radicals of the formula —B—OH are, preferably:

[0025] Possible radicals of the formula -G-(CO)n₂OH are, preferably:

[0026] Possible radicals of the formula -D-OH are, preferably:

[0027] Dyestuffs which are employed as further preferred dyestuffs of the formula (I) are those of the formula (V):

[0028] wherein

[0029] A, B, G, D, n₁, n₂ and Ct⁺ have the abovementioned meanings, and

[0030] m represents 0 or 1 and

[0031] R represents 4-nitro or 5-chloro, and in the case where m=1, the o-chlorophenylazo group is in the para-position relative to the complexing —O— group.

[0032] Preferred substituents of the polyvalent radicals A, B, G and D are, for example, those chosen from the group consisting of: NO₂, halogen, in particular chlorine, sulphonamide and C₁-C₄-alkyl.

[0033] The dyestuffs of the formula (I) which can be used according to the invention are known in most cases and can be prepared by known methods, such as are described, for example, in EP-A 066 230, EP-A 072 501 or EP-A 532 994.

[0034] The cation represented by Ca⁺ is preferably an alkali metal cation, in particular a lithium, sodium or potassium cation, an ammonium ion, the cation of an organic amine, such as, for example, that of mono-, di- or triethylamine, mono-, di- or tri-ethanolamine, N-methyldiethanolamine, N-butyldiethanolamine or N,N-diethylethanolamine, or a tetraalkylammonium, such as, for example, tetramethylammonium. A particularly preferred cation is the lithium cation.

[0035] Preferred dyestuffs of the formula I correspond to a dyestuff of the formula (Ia) (yellow)

[0036] a dyestuff of the formula (Ib) (orange)

[0037] a dyestuff of the formula (Ic) (red)

[0038] a dyestuff of the formula (Id) or (Ie) (each brown)

[0039] a dyestuff of the formula (If) (blue)

[0040] and/or the black dyestuff of the formula (Ig)

[0041] The dyestuffs of the formulae (Ia) to (Ig) wherein Ct⁺=Li⁺ are particularly preferred.

[0042] Preferred alkoxy-alcohols of the formula (II) which are mentioned are, for example, the following representatives: C₁-C₄-monoalkyl ethers of mono- and polyglycols, such as methyl glycol, ethyl glycol, propyl glycol, butyl glycol, methyldiethylene glycol, butyldiethylene glycol, methyltriethylene glycol, 1-methoxy-2-propanol, 2-methoxy-1-propanol, 1-ethoxy-2-propanol, 2-ethoxy-1-propanol, dipropylene glycol monomethyl ether means (3-(3-methoxy-propoxy)-1-propanol) and dipropylene glycol monoethyl ether means (3-(3-ethoxy-1-propoxy)-1-propanol).

[0043] Particularly suitable alkoxy-alcohols of the formula (II) are the C₁-C₄-monoalkyl ethers of glycols and diglycols and the monoalkyl ethers of 1,2-propylene glycol and of ethylene glycol, in particular monoalkyl ethers of 1,2-propylene glycol. 1-Ethoxy-2-propanol is especially preferred.

[0044] The dyestuff preparations used according to the invention can furthermore comprise

[0045] 0 to 40% by weight, in particular 20 to 35% by weight, of a cyclic ester or amide and

[0046] 0 to 5% by weight of auxiliaries customary in woodstains, such as fungicides, UV stabilizers, binders and/or surfactants.

[0047] Possible preferred cyclic esters or amides are, for example, lactones, such as 4-butyrolactone, and lactams, such as pyrrolidone, N-methylpyrrolidone, ε-caprolactam, N-methyl-ε-caprolactam and N-ethyl-ε-caprolactam.

[0048] Further water-miscible organic solvents which are customary in woodstains can also be used. There may be mentioned here in particular: lower alcohols, such as ethanol, ketones, such as methyl ethyl ketone, mono- and polyglycols, such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol and dipropylene glycol, and carboxamides, such as formamide and dimethylformamide, as well as cyclic ureas, such as 1,3-dimethyl-2-imidazolidinone.

[0049] The dyestuffs of the formula (I) are readily water-soluble. The concentration and stability of the aqueous solutions can also be increased considerably, for example, by addition of a water-miscible organic solvent.

[0050] It has been found that concentrated aqueous solutions of these dyestuffs of the formula (I), in particular those of the formulae (II) to (VIII), preferably in a mixture of water and at least one water-miscible organic solvent, are valuable woodstains with which weatherfast and lightfast wood dyeings can be achieved by various methods of application.

[0051] Possible materials for dyeing are shaped wood in the most diverse forms, including in finely divided form, such as wood shavings and sawdust, but above all wood veneers. The veneers are as a rule large-area wooden sheets of various timbers of a thickness of, in general, 0.5 to 10 mm. Possible types of wood are pine, spruce, fir, larch, Scots pine, oak, beech, ash, maple, walnut, pear, teak, mahogany, chestnut, birch, hazelnut, linden, willow, poplar or plane.

[0052] The dyestuffs of the formula (I) which can be used according to the invention can be on the surface or inside the wood material to a greater or lesser depth, depending on the nature and type of wood and depending on the dyeing conditions. Veneers are usually dyed as far as possible through the entire cross section.

[0053] The use according to the invention takes place in the customary manner, and the dyestuff preparations are preferably applied to the wood, for example, by brushing, rolling, spraying or impregnation. In the case of brushing, rolling or spraying, the dyestuff preparations are preferably used in undiluted form, while in the case of impregnation or immersion dyeing, the dyestuff preparations can be diluted with up to 300 times the amount of water.

[0054] A deeper penetration of the dyestuff into the wood material or through-dyeing of a wood veneer is as a rule achieved by immersion dyeing in closed containers. The depth of penetration is determined by the treatment time, the temperature of the dyebath and the pressure applied to the container. The treatment time can be up to 10 hours, the temperature is as a rule 20 to 120° C. and the pressure is preferably 1 to 2 bar.

[0055] The dyestuffs of the formula (I) are distinguished by a good penetration and as a rule give wood dyeings with an adequate depth of penetration or a complete penetration after just 3 hours at temperatures of up to 100° C.

[0056] In the case of immersion dyeing in a closed container, the goods to be dyed should be moistened beforehand in order to avoid deformations during the dyeing process. So that the dyestuff is fixed better in the wood, the pH of the dyebath is lowered to 5 to 4.5. After the treatment, the dyed material is generally dried in air, either at room temperature or in a circulating air cabinet at higher temperatures, preferably at 40 to 80° C. Weather-resistant dyeings which have wet-fastness properties and have a good fastness to light and overpainting are obtained in this manner using the dyestuffs of the formula (I).

EXAMPLE 1

[0057] 20 thoroughly moistened wood veneers of maple of the dimensions 2 m×1 m×1 mm are provided with spacers of polyester and transferred to a container which can be closed, and a dye liquor of 3.2 kg of a liquid preparation of the dyestuff of the formula Id and 400 l of water is poured over them. The liquid preparation itself is composed of 13% by weight of dyestuff, 40% by weight of 1-ethoxy-2-propanol and water as the balance.

[0058] The dyebath is first heated to 40° C. and the pH of the liquor is lowered to 5.0 with about 1 l of acetic acid 1:1. The dyebath is then heated up to 98° C. at a rate of 1° C. per minute, the temperature is maintained at this level for 1 hour and the dyebath is then allowed to cool to 70° C. After the sheets have been rinsed with cold water and dried in a circulating air cabinet at 80° C., a through-dyed veneer in a lightfast and weatherfast brown shade is obtained.

EXAMPLE 2

[0059] In a manner similar to that in Example 1, commercially available wood veneers are dyed with a mixture of 10 parts of liquid preparation of the black dyestuff of the formula (Ig), 1 part of liquid preparation of the orange dyestuff of the formula (Ib) and 0.5 part of liquid preparation of the brown dyestuff of the formula (Id), the preparation of the black dyestuff also comprising 20% by weight of ε-caprolactam, in addition to 45% by weight of 1-ethoxy-2-propanol. After washing and drying, black veneers with good fastness to light and weather are obtained.

EXAMPLE 3

[0060] Instead of the brown dyestuff of the formula (Id), the yellow dyestuff of the formula (Ia), the orange dyestuff of the formula (Ib) and the red dyestuff of the formula (Ic) can also be employed in the form of stable liquid formulations or mixtures of these liquid forms. At a liquor ratio of 1:25 (1 part by weight of wood and 25 parts by weight of liquor) and a dyestuff concentration of 1.5% strength (1.5 parts by weight of pure dyestuff and 100 parts by weight of substrate), coloured veneers in the yellow to red range are obtained.

EXAMPLE 4

[0061] Instead of the solvent used in the liquid preparation of the dye according to formula 1d of example 1, also a liquid preparation containing 40% by weight of dipropylene glycol monomethyl ether dyes veneer in a lightfast and weatherfast brown shade.

EXAMPLE 5

[0062] Instead of the solvent used in the black liquid preparation in example 2, 45% by weight of dipropylene glycol monomethyl ester are also used to get veneer in a lightfast and weatherfast black shade. 

1. Use of liquid dyestuff preparations for dyeing wood, wherein the liquid dyestuff preparations comprising 5 to 30% by weight, in particular 12 to 23% by weight, of a dyestuff of the formula I

 wherein n₁ and n₂ denote the number 1 or 0, X represents N or CH, Ct⁺ represents a cation and the polyvalent radicals A, B, G and D independently of one another represent heterocyclic or aromatic radicals, in particular optionally substituted phenylene and naphthylene radicals, the particular complexing —COO— or —O— group being in the ortho-position relative to the azo and azomethine group (X═CH) respectively, 15 to 90% by weight, in particular 15 to 60% by weight, of an alkoxy-alcohol of the formula (II) R—O—(-Z-O—)_(n3)—H  (II)  wherein R denotes a straight-chain or branched C₁-C₄-alkyl, Z denotes a straight-chain or branched C₂-C₃-alkylene and n₃ represents 1, 2 or 3, and 5 to 75% by weight of water are employed.
 2. Use according to claim 1, characterized in that the dyestuffs of the formula (I) are derived from the following radicals: possible radicals of the formula

Possible radicals of the formula —B—OH are, preferably:

Possible radicals of the formula -G-(CO)n₂OH are, preferably:

Possible radicals of the formula -D-OH are, preferably:


3. Use according to claim 1, characterized in that the dyestuffs of the formula (I) employed are those of the formula (V)

wherein A, B, G, D, n₁, n₂ and Ca⁺ have the meanings given in claim 1, and m represents 0 or 1 and R represents 4-nitro or 5-chloro, and in the case where m=1, the o-chlorophenylazo group is in the para-position relative to the complexing —O— group.
 4. Use according to claim 1, characterized in that at least one dyestuff of the formulae (Ia) to (Ig)

wherein Ct⁺ denotes a cation, in particular Li⁺, is employed as dyestuffs of the formula (I).
 5. Use according to claim 1, characterized in that at least one of the following compounds is employed as the alkoxy-alcohol of the formula (II): C₁-C₄-monoalkyl ethers of mono- and polyglycols, such as methyl glycol, ethyl glycol, propyl glycol, butyl glycol, methyldiethylene glycol, butyl-diethylene glycol, methyltriethylene glycol, 1-methoxy-2-propanol, 2-methoxy-1-propanol, 1-ethoxy-2-propanol, 2-ethoxy-1-propanol, dipropylene glycol monomethyl ether means (3-(3-methoxy-propoxy)-1-propanol) or dipropylene glycol monoethyl ether means (3-(3-ethoxy-1-propoxy)-1-propanol).
 6. Use according to claim 1, characterized in that the liquid dyestuff preparation furthermore comprises 0 to 40% by weight, in particular 20 to 35% by weight, of a cyclic ester or amide and 0 to 5% by weight of auxiliaries customary in woodstains.
 7. Use according to claim 1, wherein the liquid preparation comprises 20 to 90% by weight, in particular 25 to 60% by weight of an alkoxy-alcohol of the formula II wherein n₃ represents 2 or 3 is employed.
 8. Use according to claim 1, for dyeing wood, characterized in that the possible types of wood are the following: pine, spruce, fir, larch, Scots pine, oak, beech, ash, maple, walnut, pear, teak, mahogany, chestnut, birch, hazelnut, linden, willow, poplar or plane.
 9. Process for dyeing wood, characterized in that the dyestuff preparations according to claim 1 are applied to the wood by brushing, rolling, spraying, impregnating or immersion, if appropriate after 300-fold dilution with water. 